dm snapshot: use per device mempools

Change snapshot per-module mempool to per-device mempool.

Per-module mempools could cause a deadlock if multiple
snapshot devices are stacked above each other.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/md/dm-snap.h b/drivers/md/dm-snap.h
index 70dc961f40d8..292c15609ae3 100644
--- a/drivers/md/dm-snap.h
+++ b/drivers/md/dm-snap.h
@@ -161,6 +161,8 @@ struct dm_snapshot {
         /* The last percentage we notified */
         int last_percent;
 
+        mempool_t *pending_pool;
+
         struct exception_table pending;
         struct exception_table complete;